For a dentist or a dental technician, one of the main difficulties in making a working physical model of the teeth, including the inter-occlusal relationship between the jaws (also known by the term “master cast” or “working cast”), lies in respecting the position of a patient's artificial jaws when the teeth are in Centric Occlusion position. Separate molding of the upper and the lower teeth followed by the manual articulation of the two parts is a constant source of error. The precision of the cast depends on several factors, including, inter alia, the accuracy of the impressions and wax bites, the material from which the cast is constructed, and the identification of the anatomic. In addition, traditional methods using pins do not prevent linear expansion of the cast. This can result in the deformation of the new teeth that do not correspond perfectly to the original. Thus, the more precisely the working cast reproduces the anatomy of the mouth, the more accurate will be the spatial position, and the static and dynamic relationships. This provides a better possibility of producing a biomechanically acceptable restoration.
In order to reproduce with high precision the mechanical equivalent of functional and non-functional movements within the mouth, articulators (also known by the term “occluding devices”) have been and still are under development. The articulators are used to precisely hold models of a patient's upper and lower teeth, so a dentist can study their bite or make a restoration.
Articulators are primarily used when a crown needs to be prepared. According to current practice, after diagnosing in a patient the need for a crown or a bridge, the dentist cuts the tooth to be reconstructed by the crown or bridge and prepares two impressions and a wax bite of the patient's jaws. One impression is of the area prepared for the crown and the surrounding area. The other impression is of the opposite jaw. A wax bite is used to record the spatial relation between the jaws at occlusion. Based on the impressions, wax bite and written instructions of the dentist, a technician prepares in a lab the corresponding plaster jaws which are trimmed and mounted on an articulator. Using the wax bites, the spatial relation between the jaws is determined. At this stage, the tooth within the preparation to be reconstructed is temporarily separated from the plaster so that the area with the anatomic information (the area defining the anatomic contour) and the finish line are exposed. The finish line is typically marked manually by the lab technician in ink on the preparation and a crown is built based on the resulting preparation. The quality of the crown prepared is examined by placing the crown on the preparation in the articulator and verifying that there is a good occlusion of the crown with the opposite teeth. If in the affirmative, the crown is sent to the dentist for placement on the preparation in the patient's mouth.